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Unlike European outlets, Japanese outlets look just like the standard 2-prong US outlet. However, the Japanese have a 100V system, whereas the US has a 120V system. Most electically powered items can handle voltage that is not precisely what is specified, but I'm not sure wether this will cause problems for some things like laptops and tablets. I just looked at my smartphone's charger and laptop transformer since they were within reach, and both list ratings for 100V-240V input, so I would think either would work fine in Japan. I suggest you check all of your power supplies and make sure they are rated for 100V input, and you will probably be ok. I'm not sure about Korea though!